South Island residents have been given an impromptu light show with a large meteor-like object breaking up in the night sky.

Reports of a "spectacular" minute-long flash across the sky were flooding in from across the south on Tuesday night, Weatherwatch said.

Video footage showed the object passing through the atmosphere at about 6.30pm before breaking up into several pieces.

"I just saw a huge streak of light in the sky north of Dunedin. Something entered the atmosphere then created a big tail behind it. At one point it got brighter and later broke into smaller pieces," one person told Weatherwatch.

But former Mount John Observatory astronomer Alan Gilmore told Radio NZ the object took too long to go across the sky to be a meteor and was more likely space-junk or a piece of a satellite.

He said the large object would have been travelling at about 30,000km/h.

"The only one other report I've ever heard from New Zealand, that was about 10 years ago, that was definitely another rocket, casing-type thing," he said.